1. Field of the Invention
The present invention relates generally to electroplating processes utilized in the manufacture of thin film devices, and more particularly to mushroom plating process steps utilized in the manufacture of thin film devices such as magnetic read/write heads, as well as devices created using such process steps.
2. Description of the Prior Art
Electroplating process steps are utilized to create metallic structures and electrical interconnects in the manufacturing of many types of thin film devices. Such thin film devices include integrated circuit devices, and thin film magnetic read/write heads utilized in hard disk drives, micro-electromechanical devices and the like.
As is well known, photolithographic techniques are utilized in the process steps that are utilized to create the electrochemically plated metallic structures, and a significant limitation on the use of photolithographic techniques can occur where the hole or trench that is created is both deep and narrow, that is, it has a high aspect ratio. In such situations it is difficult to accurately create the trench or hole, and it is likewise difficult to effectively electrochemically plate into the high aspect ratio trench. Prior art attempts to overcome these problems have utilized overplating techniques, also termed mushroom plating. These mushroom plating techniques may involve the utilization of a shallower trench than is required for the desired height of the metal component structure, followed by the overplating of the trench, such that a generally mushroom shaped cap is formed in the area on top of the trench. The relatively shallow trench facilitates good electrochemical plating at the base of the trench, and the mushroom plating facilitates the formation of the tall component structure that is desired. Likewise, in fabricating complex shaped metal structures, such as the yoke of the second magnetic pole of a thin film magnetic write head, some portions of the photoresist trench may be significantly deeper than other, shallower portions of the trench. In this situation, when the metallic plating is performed to a depth that fills the deeper portions of the trench, overplating occurs in the shallower trench areas. With specific regard to such write head magnetic poles, typically the pole tip area is formed with a deep trench, whereas the wider yoke area is formed with a shallower trench. In the plating process, the pole tip area is formed entirely within its deeper trench, whereas overplating occurs in the yoke area, leading to the formation of a mushroomed yoke.
In the prior art photolithographic plating techniques, following the plating step the photoresist is removed utilizing a wet etch chemical removal step. Significant problems are incurred at this point in the prior art mushroom plating processes. Specifically, where the photoresist is chemically removed, an empty space is created beneath the overhanging portions of the mushroom head. Thereafter, in following process steps, unwanted redeposition of reactive species and particulates can occur beneath the overhang, and it is difficult if not impossible to remove the redeposited material beneath the overhang. Additionally, when the device is finally encapsulated at the end of the manufacturing process, voids are created beneath the overhang which are detrimental to the performance of the manufactured devices. The process of the present invention eliminates the redeposition and void creation problems previously incurred in employing mushroom plating techniques.
A first embodiment of the mushroom plating process of the present invention starts with an overplated component which includes an enlarged mushroom head having outer portions which overhang a resist layer. The next step in the first process embodiment is a heating step in which the resist layer is hard baked. Thereafter, using a dry etch process, such as a reactive ion etch (RIE) process, the hard baked resist layer is removed in all areas except beneath the overhang of the mushroom head. The area beneath the overhang thereby remains filled with hard baked resist. Thereafter, the device is ultimately encapsulated such that no voids and/or redeposition problems exist under the overhang due to the presence of the hard baked resist. In an alternative process embodiment of the present invention the dry etch process is conducted first upon the resist layer, such that the resist layer is removed in all areas except under the overhang. Thereafter, the device is baked, such that hard baked resist remains beneath the overhang. Ultimately, the device is encapsulated and no voids or redeposition problems exist beneath the overhang due to the presence of the hard baked resist. Devices that are manufactured utilizing the processes of the present invention are also included within the invention. While not intended to be limiting in any manner, one such device is a thin film magnetic head wherein the yoke portion of a magnetic pole is formed utilizing the mushroom plating techniques of the present invention. Another mushroom plated component found in many devices is a mushroom plated electrical interconnecting stud that is formed utilizing the process steps of the present invention.
It is an advantage of the mushroom plating process of the present invention that mushroom plating can be conducted without incurring redeposition and void problems.
It is another advantage of the present invention that improved mushroom plated component can be obtained without significant additional manufacturing process steps.
It is a further advantage of the present invention that the space under the mushroom head overhang is filled, such that redeposition does not occur, and voids do not occur during encapsulation.
It is yet another advantage of the present invention that an improved mushroomed yoke structure is provided for thin film magnetic write heads.
It is yet a further advantage of the present invention that improved mushroom plated electrical interconnect studs are provided for thin film devices.